[HeyLaughingBoy]

But from your manager's perspective, you probably do know. You know if it will take more than or less than a year. You know if it will take more than or less than a month. You have some idea of what needs to be done. You have some idea of what parts of it you don't know, etc.

One of the most important things I've learned about estimating is first asking how accurate an estimate is needed. Often the person just wants to know "can I have it tomorrow, or will it take 3 months?"

[anthonyb]

Depending on the task, it might not actually even be possible. Or, it's doable but not without rewriting major libraries or buying hundreds of servers.

[HeyLaughingBoy]

And all those things you've just said are valuable pieces of information to the person asking!!!